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Mini-talks: The Machine Intelligence Landscape: A Venture Capital Perspective by David Beyer. The future of global, trustless transactions on the largest graph: blockchain by Olaf Carlson-Wee. Algorithms for Anti-Money Laundering by Richard Minerich.

Rails Caching Reloaded With EHCache

Rails 2.1 brings new caching features which makes it very easy to cache any values including models. Apart from the basic File, Memory and DRb stores, Memcached was the only solution to do shared memory cache. (J)RoR can now count on the popular Java distributed cache EHCache as part of its new Cache stores thanks to Dylan Stamat.

In the JEE world, debates around using EHCache vs. Memcached for second level cache have long been raging. While Memcached is popular in the LAMP and RoR world (Linkedin.com will switch to it soon), EHCache was adopted by projects like Spring or Hibernate. In an effort to migrate an existing application from MRI Ruby to JRuby, Dylan Stamat ported EHCache to JRuby adding EhcacheStore as a new cache Store.

In the MRI world, we use memcached, which is a Ruby interface to the libmemcached C client. It is one of the only Ruby libraries that currently supports consistent hashing, which is a requirement for our production environment. When preparing for JRuby, we had a different set of options. One was writing our own hooks into libmemcached via JNA, JRuby FFI, etc. The other was to look for another cache solution in Java, and Ehcache was definitely on top of the list.

Another option for using consistent hashing with memcached and JRuby would be to use the spymemcached client. The spymemcached client is an asychronous single-threaded client that has proven to work extremely well in the hibernate-memcached project. I have also used the spymemcached client in other projects and its performance was outstanding.

As you know, the 'page caching' is by far the fastest caching system in Rails (like 2 orders of magnitude faster than hitting a fragment cache). But unfortunately, standard Rails page caching tends to be harder on J2EE serveurs that sometimes behave really differently from an Apache front end for instance. Especially there is an issue with static files colliding with dynamic requests pathes (just normal for standard rails page caching) but that are redirected agressively on J2EE servers unless you hack the app a little bit specifically for a J2EE deployment.

Also, file based page caching is hardly convincing, even if J2EE servers have a memory cache of the static files. Indeed, there can be latency, disk access, it's not very easy to scale in cluster or to have something close to transactional.

EH Cache would be a very great fit for all that. And Ideally it would be as transparent as possible so we avoid to much J2EE specifics here. Still, as serving pages directly from J2EE server tends to be two orders of magnitude faster than entering a JRuby+Rails runtime, it would be really great to tweak the JRuby-Rack servlet filter so that EH-Cached cached pages get served from directly from that servlet filter without even hitting the JRuby on Rails runtime! It would be a bit like the current file base page caching system but I think this would be faster, easier to scale and won't be screwed up with path collision. Any thought?

Hey Raphael ! That's a great idea, and would love to get a memory option for page caches into JRuby/Rack at some point. I'm following the thread you and Nick Sieger are having in jira.codehaus (2832), and will chime in when I get a chance :) Thanks !